Sylvania



May 1, 192 8.

H. w. WILLIAMS MOTOR CONTROL SYSTEM Original Filed Sept. 8. 1925 vW T wL 0 f 2 mooo 0 w o 0 o Reias ued M... 1, 1928.

@UNIT D STATES PATENT OFFICE.

HAROLD W. WILLIAMS, OF EAST I'ITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WEST-INGHO'USE ELECTRIC & MAN UFACTUBING COMPANY, A CORPORATION OF PENN-srnvama MOTOR-CONTROL SYSTEM.

Original Ho. 1,549,698,-dated August 11, 1925, Serial No. 661,588, filedSeptember 8, 1923, Application for reissue filed August 10, 1927. Serial110. 212,114. Y

I My invention relates to motor-control sys-,

tems and it has particular relation to .such systems of control as areemployed in connection with elevators, machine tools and similarmachines;

An-object of my invention is to provide means forcontrolling the speedand the torque of an alternating-current motor of the two-speed typecommonly employed in ele vator service and having separate low andhigh-speed windings.

My invention is more particularly applicable to the control of atwo-speed'motor of a well-known squirrel-cage type.

In the operation of alternating-current motors of the type hereindescribed,;it is common practice to start the motor by connecting itslow-speed winding to the source and provide means for ensuring arelatively weak excitation of the low-speed windings.

Next, the low-speed windings are shunted and the excitation of thehigh-speed .windings is increased'to its maximum value.

In systems heretofore known it has been essential that a definitesequence of operation of the transition switches be maintained:otherwise the motor either lost torque or the supply circuit wasshort-circuited, depending upon whether the corresponding .phases of thetwo windings wereinitially'conn'ected in series or in parallel relation.As is hereinafter described, with my system the sequence of operation ofthe transitionswitches is not material, neither loss of torque nor shortcircuit being caused, regardless of the sequence of operation.

To efiect deceleration of the motor, the speed windings are firstconnected in the -plfeviously named parallel relation, after which thehigh-speed windings are de-en'ergiz jed and finally the excitation ofthe lows'p'd windin is increased to obtain a mindesira 1e operationspeed. Again, ppyelverpthe sequence .of transition is mm no. j a

been My invention willbe described in connection with the accompanyingdrawing, in.

which Figure 1 is a diagrammatic representation of atwo-speed,three-phase, alternating-current squirrel-cage motor employedin connection with my invention,

. Fig. 2 is a diagrammatic representation of v the main circuits andapparatus embodying my nvention,

Fig. 3 1s a diagrammatic representation of i the control circuits thatare employed in the operation of the system shown in Fig. 2, and Fig. 4isa sequence chart indicating the operation of switches employed in Fig.2.

Referring to the drawing, a two-speed alternating-current motor 1 isprovided with low-speed primary windings 2' and high-' speedprimary'windings 3. These windings are connected in series relation witha plurality of reactors 4: and 5, which are respectively employed forlow-speed and for high-speed operation- Resistor sections 6 are arrangedfor connection in circuit with the high-speed windings 3 through aswitch 7. A three-pole switch 8 provides means for shunting thehigh-speed windings 3 and rendering the low-speed windings 2 effective.Double-pole reversing switches 9 and 10 are Poremployed in the customarymanner. tlons of the -low-speed.-reactors 4; may be shunted by adouble-pole switch 11 that is provided with a retarding device 12.

1 "Also, a double-pole switch '13 is arranged.

for shunting resistor sections 6. This switch is also provided withretardi'n means. Both switches 11 and 13 are retar ed only in closing.The various switches are operated by means'of a reversible master switch23 of a familiar type having a plurality of operating positions a, b, cand d. A source of power-supply for the motor comprises lineconductorsl, 15 and 16. I have n illustrated connections for athree-phase induction motor, but, of course, a two-phase motor or motorsof other suitable types may be similarly employed.

Assuming the apparatus to be in its inoperative or illustratedpositions, the motor 1' ma be operated in an upward direction 7 actuatinthe left. In position a see sequency chart, Fig. 4) a circuit is provithe master switch 23 to ed for eflectin the closure of reversing switch9 and CW! in a well-known manner.

speed switch S. 7 Power is then supplied to the motor windings 2, withreactors 4 in circult therewith. If master switch 23 is maintained inposition a, switch 11 will close to shunt a portion of reactors 4,whereby the motor is provided with sufiicient torque to start thedesired maximum load. A lightload may be started prior to the closure ofswitch 11. However, the primary object of the additional sections ofreactors 4 will hereinafter appear.

\Vheu the master switch 23 is actuated toward posit-ion I), switch 7,may close prior to the opening of switch 8, whereupon highspeed windings3 are connected, through resistor sections 6 in parallel relation tolowspeed windings 2. This osition affords a transition period or, ifdesired, may serve as an operating position in which the motor operatesat a speed intermediate its minimum and maximum speeds, depending uponthe degree of excitation of the low-speed windings 2.

When the master switch 23 is moved to position I), switch 8 opens andthe motor is further accelerated in accordance with the excitation ofthe windings 3. Finally switch 13 closes'to shunt resistors 6, whereupon the motor operates at its maximum speed.

It should be noted, in .connection with the foregoing description, thatthe motor speedwindings are at no time disconnected nor is the powersupply interrupted so that a fairly uniform torque is developed by themotor in accordance with the arrangement of the reactors and resistorswhich are, of course, designed for limiting the currents The motor isdecelerated by returning master switch 23 toward the ofi positions,passing through position a. Switch 8 is reelosed, re-establishing theabove-described parallel relation of motor windings 2 and 3, and, uponthe re-opening of switch 7, the

high-speedwindingsti are de-energized and the motor is furtherdecelerated, since only the low-speed windings 2 are then energized.Switch 11 starts to close but is re-\ tarded for a suflicient period,whereby the torque of the motor, which is for the moment operating aboveits lower synchronous speed, is suitably reduced. The effect of theadditional reactor sections 4, which are controlled by switch 11, is toprevent a too abrupt change in the speed of the motor, occasioned by itsregenerative action. Sulficient time is allowed for the closure ofswitch 11 so that the motor speed is first suitably reduced. Under slowspeedconditions, reactors 4 have little effect upon the speed regulationof the motor so that it is, ordi- -narily, unnecessary to provide meansfor entirely shunting these reactors from the circuit. If it isdesirable tooperate the motor According to my invention, I am enabled toaccelerate and decelerate a motor having separate high and low-speedwindings without disconnecting; these windings, whereby a fairly uniformtorque is obtainable and, cons sequently, smooth and flexiblespeed'control. Also, the switching arrangement is such that the lineconductors cannot be short-circuited by failure of any of thespeed-controlling switches to function.

In the arrangement of apparatus, as illustrated in- Fig. 2, it ispossible to provide for a different sequence of operation and to obtainstill other operating speeds as, for example, when both the high andlow-speed switches 7 and 8 are open, and the motor windings are allconnected in series relation. Resistors may besubstit-uted in place ofreactors 4 and 5, when desirable, but I prefer to employ the arrangementillustrated, particularly for hoisting applications,

Operation of the motor in a reverse direc-' tion is obtained in a mannersimilar to that described above, upon the closure of reversing switch 10in place of reversing switch 9 by the manipulation of master switch 23to the right, through positions .0 and d, as will be readily understood.

I have described and illustrated my invention in simple form, butvarious modi fications may be made therein Without departing from thespirit and scope thereof.

I claim as my invention: 1. The method of accelerating analternating-current motor having low and highspeed' windings connectedin series relation,

which consists-in shunting the high-speed windings, connecting said highand lowspeed windings in parallel relation, diminishing the effect ofsaid low-speed windings and finally shunt-ing said low-speed wind- IDES.

2. The method of accelerating an induction-motor having low andhigh-speed windings connected in series relation, which consists inenergizing the low-speed windings,

connecting said low and high-speed windings in parallel relation,lessening the effect of said low-speed windings, and finally,

shunting said low-speed windings.

3. The method decelerating an alternating-current motor having low andhighspeed windings connected in series relation, which consists inconnecting the low and high-speed windings in parallel relation when theeffect of the low-speed windings.

is relativelvweak, disconnecting said highspeed windings andstrengthening the effect of the low-speed windings.-

4. The combination with an alternatingcurrent motor having low' andhigh-speed Windin connected in series relation and ing said windings,

' and for connecting said windings t e reactors alternating in positionwith said windings, 'of'means for selectively shunting said windings andfor connecting said windings in parallel relation without interruptingthe motor circuit.

5. The combination with an alternating-v current motor having low andhigh-speed windings connected in series relation, and reactorsalternating in position with said windings, of means for selectivelyshunting said windings and for connecting said windings in parallelrelation without disconnecting said windings.

6. The combination with an alternatingcurrent motor having low andhigh-speed windings connected in series relation, and current-limitingmeans alternating in position with said windings, of means forselectively shunting said windings and for connecting said windings inparallel relation without interrupting the motor circuit.

7. The combination with an alternatingcurrent motor having low andhigh-speed windings connected in series relation, and current-limitingmeans alternating in position with said windings, of means forselectively, shunting said windings and for connecting said windings inparallel relation without disconnecting said windings.

8. The combination with an alternatingcurrent motor having low andhighspeed windings connected in series relation, and reactors in circuitwith said windings, of means for'selectively shuntin said windings inparallel relation without interrupting motor circuit. 9. In a controlsystem for multi-phase alternating current motors having high-speedwindings and low-s eed windings, a source of power, a switch or eachwinding, a. current-limiting device, and means for connectsaid switchesand said device to said sourcewhereby transition from one winding to theother winding may be made with at least one of said windings active atall times regardless of the .sequence of operation-of said switches.

10. In a control system for multi-plhase alternating current motorshavin ighspeed windings and low-speed win ings, a source of power, aswitch for each of said windings, means for selectively opei'ating saidswitches, a current-limiting device, and

means for connecting said windings, said switches and said device tosaid source of power whereby operation of said switches will connectsaid windings in series relation or in parallel relation or eitherwinding alone to said source of power. 7

11. In a control system for multi-phase alternating current motors havinhighspeed windings and low-speed win ings, a source of power, a switchfor each' of said windings, means for selectively operating seriesrelation, said v ces being severally dis said switches, acurrent-limiting device, and

means for connecting said windings, said switches and. said device tosaid source 0 power whereby operation of either of said switches willconnect the correspond mg windings to said source. exclusive of theother, operation of both of said switches will connect said windings tosaid source in parallel relation and non-operation of both of saidswitches willconnect said windings to said source in series'relation.

12. In a control system for multihase alternating current motors, havinga lighspeed winding and a'low-speed winding, 2.

means connectto said 'wmdlngs ing said source of-power at will, meanssaid phase of series relation with thecorresponding use of saidlow-speed winding, a, currentimiting device connected" therebetween,means multi-phase source of power,

for shunting each phase of said high-speed winding and its associatedcurrent-limiting device, and means for connectin all of the phases ofthe high-spec windings at oints between for permanently connecting saidhigh-speed windin in together the high-speed windings I an theirassociated current-limiting devices.

13. In' a control system for multi-phase alternating current motorshaving a high-.

speed winding and a low-speed winding, 3. multi-phase source of power,means for connecting said source of power ings at will, meanspermanently connecting each phase of said high-speed winding in to saidwindseries relation with the corresponding hase means.

14. In a control system for multihase alternating current motors havinga ighspeed windin and a low-speed winding whereby transition from onewinding to the other'may be accomplished without loss of torque andwithout short-circuit, the combination of a plurality ofcurrent-limiting devices, means for permanently connecting correspondingphases of said high-speed windings and said low-speed windings incurrent-limiting deosed therebetween, switch means for simu taneouslyshunting the high-speed phase windings and their associatedcurrent-limiting devices, and switch means for simultaneously connectingto- Phases f said high-speed windings and said ow-speed windings inseries relation, said reactors being severally disposed therebetween,switch means for simultaneously 1!; shunting the high-speed phasewindings and their associated reactors, and switch means forsimultaneously connecting together all of the phases of said high-speedwinding at points between said windings 20 and said reactors.

' HAROLD W. WILLIAMS.

